The retina is the light-sensitive layer of tissue at the back of the inner eye. It acts like the film in a camera. Images come through the eye's lens and are focused on the retina. The retina then converts these images to electric signals and sends them via the optic nerve to the brain.
The retina is normally red due to its rich blood supply. An ophthalmoscope allows a health care provider to see through your pupil and lens to the retina. If the provider sees any changes in the color or appearance of the retina, it may indicate a disease.
Anyone who experiences changes in sharpness or color perception, flashes of lights, floaters, or distortion in vision should get a retinal examination.
Yanoff M, Cameron D. Disorders of the visual system. In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 431.